KCS Monitor R&D SYSTEM USER'S GUIDE - Klippel GmbH - www.klippel.de

R&D SYSTEM USER’S GUIDE

 KCS Monitor

 Klippel GmbH

July 23, 2021
Copyright © 2000-2021 Klippel GmbH
Mendelssohnallee 30, 01309 Dresden, Germany
www.klippel.de

Contents
 1 KCS Monitor Tutorial.............................................................................................. 1
 1.1 Introduction ........................................................................................................................ 1
 1.2 Requirements ..................................................................................................................... 1
 1.3 Tutorial 1 – Starting KCS ..................................................................................................... 2
 1.4 Tutorial 2 - Viewing data .................................................................................................... 3
 1.5 Tutorial 3 – Switching Control Modes ................................................................................ 4
 1.6 Tutorial 4 – Alignment and Equalization ............................................................................ 5
 1.7 Tutorial 5 – Protection and Limiter .................................................................................... 7
 1.7.1 Short Theory .............................................................................................................. 7
 1.7.2 How to Setup Protection and Limiter ....................................................................... 8
 1.7.3 Protection with separate ANC input channel ......................................................... 10

 2 KCS Monitor Reference ........................................................................................ 13
 2.1 KCS Setup Parameters ...................................................................................................... 13
 2.2 Result Windows ................................................................................................................ 15
 2.2.1 Nonlinear Curves ..................................................................................................... 15
 2.2.2 x(t) Displacement .................................................................................................... 15
 2.2.3 u(t) Voltage, i(t) Current .......................................................................................... 16
 2.2.4 ∆Tv(t)Temperature, P(t) Power ............................................................................... 17
 2.2.5 fs(t) Resonance Frequency ...................................................................................... 18
 2.2.6 Distortion Components ........................................................................................... 18
 2.2.7 Z(f,x=0) Impedance Magnitude ............................................................................... 19
 2.2.8 Protection................................................................................................................ 19
 2.2.9 H(f) Sound Pressure................................................................................................. 20
 2.2.10 Linear Speaker Parameters ..................................................................................... 21
 2.2.11 State ........................................................................................................................ 22
 2.2.12 Setup ....................................................................................................................... 23
 2.3 Alignment ......................................................................................................................... 23
 2.4 Hardware Connection ...................................................................................................... 25
 2.4.1 Klippel Analyzer 3 .................................................................................................... 25
 2.4.2 Nuvoton Audio Development Platform .................................................................. 26
 2.5 Things you should never do.............................................................................................. 27
 2.6 Troubleshooting ............................................................................................................... 28
 2.6.1 Message Boxes ........................................................................................................ 28
 2.6.2 Selected warning messages .................................................................................... 28
 2.6.3 Other Issues............................................................................................................. 29

 3 Index ................................................................................................................... 31

Klippel R&D System Contents  I

1 KCS Monitor Tutorial

 1.1 Introduction
Klippel Controlled Sound is an adaptive software solution featuring nonlinear speaker control, active
speaker protection, linear and nonlinear distortion reduction, automatic system alignment and much
more. KCS Monitor is a software module running in the Klippel dB-Lab framework which is used for
evaluating this technology. It allows to communicate with a supported KCS hardware platform and is
used to both set up the KCS real-time processing software and to read comprehensive diagnostics
information from it.
For running the KCS Monitor initial data for the particular speaker under test is required. Find
information about creating initial data in [KCS2] Manual KCS-ID Parameter Identification.

 Lab KCS Server

 Initial Identification zip file
 KCS-ID

 Initial Parameter
 Creation

 KCS Evaluation kdbx File
 KCS Monitor

 Overview KCS landscape

Two versions of KCS Monitor are available:
  KCS Monitor
  KCS Monitor Pro
The standard KCS Monitor module does not require a hardware dongle and supports all KCS
hardware platforms except the Klippel Analyzer 3 (KA3). For evaluating KCS on the KA3, if advanced
customizations for the KCS setup are needed or long-term tests have to be performed, the KCS
Monitor Pro module has to be used.

 1.2 Requirements
  Klippel dB-Lab version >= 210.918
  KCS Monitor operation comprising initial data (received from the KCS Server, Klippel GmbH
 or a Klippel partner company)
  KCS hardware platform
  Nuvoton A6 version >= 3.00 (only NAD - Nuvoton Audio Development platform)

Klippel R&D System KCS Monitor Tutorial  1

1.3 Tutorial 1 – Starting KCS
Hardware Setup
Setup the KCS target hardware platform for KCS on-line processing.
  KCS running on KA3: See section 2.4.1. Make sure that your audio source is connected to the
 IN1/2 XLR plug
  KCS running on NAD: Refer to section 2.4.2/0 or the NAD Quick Start Guide provided by
 Nuvoton. Make sure that the output audio device on your PC is set to Nuvoton Audio
 Development Platform.
  KCS running on Klippel APE Evaluation Board: see corresponding user manual.

Open Initial KCS data
Initial KCS data comprising speaker and target platform parameters is required to start KCS:
  Use the KCS-ID module (KA3 device required) and download the according KCS Monitor
 operation from the KCS Server (see [KCS2] Manual KCS-ID Parameter Identification)
  If you are using a NAD board as KCS target platform and you have received a reference
 speaker together with the hardware, initial KCS data for this speaker is provided by Nuvoton
Open the Klippel dB-Lab database comprising the KCS Monitor operation holding the initial KCS data
belonging to your speaker.

Upload KCS Data to the Hardware Device

Property page of KCS Monitor

Open the KCS Monitor’s property page by right-clicking on the operation  Properties or marking
the operation and press [Alt]+[Return].

For KCS platforms connected via a serial port (e.g. NAD), press Scan Connected Devices to update the
available COM ports.

Within the properties window, press ‘Connect to Device’ to synchronize the KCS setup of software
module and hardware. Refer to 2.6.1 in case of any issues.

2  KCS Monitor Tutorial Klippel R&D System

Starting KCS on-line processing
Start the KCS real-time processing by pressing in the toolbar. This will start the audio output and
the collection of diagnostic data. In case any errors or warnings appear, see section 2.6.

Play Audio
You can now verify that everything is connected correctly by playing music or other audio signals.

Note: The main benefits of KCS are experienced at high voice coil excursion. Apply a bass boost
(alignment) for achieving best bass performance and for driving the speaker to its physical limits (see
1.6).

While playing audio signals, you can observe loudspeaker states and parameters (see 1.4), evaluate
KCS performance by switching KCS on and off (see 1.5) and perform measurements (see guidelines in
[KCS4] KCS Evaluation Tutorials). If any issues occur, see 2.6.

Stopping KCS on-line processing
The KCS Monitor operation can be terminated by pressing the green check mark in the toolbar. After
finishing, a message box ‘Terminate KCS on-line Processing?’ pops up which allows you to run the
KCS on-line processing in standalone mode without a PC connection.

 1.4 Tutorial 2 - Viewing data
KCS continuously monitors loudspeaker parameters and compensates the effects of ageing, fatigue,
temperature changes and humidity. During the execution of KCS Monitor, diagnostic data such as
time-variant loudspeaker parameters and states are constantly uploaded from the KCS hardware
platform.

Klippel R&D System KCS Monitor Tutorial  3

Default Windows of KCS Monitor Standard carrying diagnostic data

The default windows and most important on-line diagnostic information shall be introduced here.
Find more detailed documentation about the results in 2.2.
 1. Force Factor Bl(X) – Force factor Bl over the entire displacement range covered during the
 last second (black curve) and covering the whole identified working range [-xmax,xmax] (red
 curve).
 2. Voice Coil Displacement – The green curves represent the predicted maximum positive and
 negative peak displacement. The pink curve indicates the voice coil’s rest position which
 should be close to zero if the DC Stabilization is turned on. In case the KA3 is used, peak and
 bottom laser signals are displayed here as well. The fat red curves shows the current
 excursion limit Xprot used by the mechanical protection system.
 3. Voltage and Current – Peak and RMS voltage and current.
 4. Voice Coil Temperature and Electrical Power – Voice coil temperature (based on both
 measurement and simulation) and measured electrical power.
 5. Protection – This window shows the degree of activation of the thermal (G cu - red) and
 mechanical (G cx - green) protection systems.
 6. State Table – This table shows important state information and warnings of the KCS
 processing. Buttons for switching KCS on and off are available in this window (see next
 section for more explanations).

GENERAL INFORMATION: Time Cursor

In all windows where the x-axis denotes the measurement time, a bold black time cursor is located
at the far right. This time cursor can be dragged using the mouse or be moved by clicking into the
chart while holding [Ctrl].

When you move the time cursor you see the other windows getting updated to reflect the state of
the device under test (DUT) at the selected time. This allows to review all the recorded history data
and parameter variances over time.

 1.5 Tutorial 3 – Switching Control Modes
 KCS can be switched on and off using the according buttons in the State window during
 runtime. See descriptions below

KCS ON (Nonlinear Control): Full Nonlinear Control with active protection, distortion compensation,
linear and nonlinear inductance compensation and voice coil stabilization. System alignment is
applied.
KCS OFF+EQ (Equalization only): No mechanical protection and no nonlinear distortion
compensation. Time-variant parameters and the linear inductance are compensated. System
alignment is applied.
KCS OFF (Bypass Control): No alignment, no mechanical protection and no distortion compensation.
The thermal protection is still active.

4  KCS Monitor Tutorial Klippel R&D System

Attention: The transducer can be destroyed in KCS OFF modes as the mechanical protection system
is switched off! When switching to these modes from KCS ON mode, make sure that the mechanical
protection system is not active.

 1.6 Tutorial 4 – Alignment and Equalization
This tutorial describes how to tune the small signal response of the KCS speaker system.

 f0 alignment
 type

 Audio Signal Equalizer
 Alignment Protection Linearization Output Limiter
 (e.g. A6)
 KCS Audio Path
The automatic alignment feature of KCS allows to tune the low frequency response of the system to
a desired transfer function with defined cut-off frequency f0 and filter type (such as Butterworth or
Chebychev). Due to the adaptive compensation of time-varying speaker parameters, this transfer
function will be maintained over the whole lifetime of the transducer. The Alignment is used to
  apply a bass boost to a sealed box system shifting the cut-off frequency 1-2 octaves below
 the system resonance frequency fc
  match an arbitrary speaker to a given sealed or vented box enclosure and achieve your
 desired transfer behavior
  reduce voice coil excursion below cut-off frequency / subsonic filter
Any additional equalization can be applied before the KCS processing, e.g. using Nuvoton’s A6 tool
(NAD platform only).

Alignment Transfer Functions. Applying alignment sealed box (left) and a passive radiator box system (right). The green
curves represent the target response.

Tips and Requirements for Setting Alignments
  Boosting low frequencies leads to large gains in the alignment filters. To avoid clipping, the
 input signal must be attenuated by the maximum alignment filter gain manually if the NAD
 evaluation board is used to avoid clipping.
  Lowering the cut-off frequency by more than two octaves (sealed systems) or far below
 port/enclosure resonance (vented/passive radiator systems) is not recommended due to the
 potentially drastic increase of peak voltage and displacement demands.

Klippel R&D System KCS Monitor Tutorial  5

 To prevent low-frequency content from producing displacement and power consumption
 without significant sound pressure contribution, it is highly recommended to select at least a
 4th (sealed box) or 6th (vented/passive radiator) order alignment.
Find more detailed information and theory about the alignment filters under 2.3.

How to set an Alignment – Workflow
 1. Connect the KCS hardware and open the KCS Monitor operation including initial data for the
 particular speaker. Connect to the device (see 1.3) to be able to change KCS setup
 parameters on the KCS Monitor’s property page. KCS must not be running on the device yet.

 2. Choose a desired transfer behavior (e.g. Butterworth 6th order) and a low cut-off frequency
 (e.g. half of the system resonance frequency found in the window Linear Speaker
 Parameters). You can see the desired transfer function by
 a. (NAD platform) opening the window Sound Pressure Hpfar(f).
 b. (other platforms) pressing the Calculate Alignment button in the KCS Monitor’s
 property page. A new operation is created which comprises the according transfer
 function.

 3. (NAD platform only) Compensate the alignment gain to avoid clipping:
 a. Start the Nuvoton A6 tool.
 b. In A6, connect to the device via Communication  UART (Mutex). Select the same
 COM port as set in the KCS Monitor.
 c. Go to the Limiter category and set the limiter gain in the A6-Tool to compensate for
 the alignment gain

 4. Run the KCS Monitor operation and start playing music and/or test signals.

Equalization
After the alignment is applied, the overall frequency response can be adjusted by using the A6 tool
or other external tuning software running on the PC or on another hardware. It is recommended to
use the Klippel QC system for measuring the frequency response, see document [KCS4] KCS
Evaluation Tutorials.

6  KCS Monitor Tutorial Klippel R&D System

Attention: (A6 tool only) Make sure to not only compensate the maximum gain of the alignment as
explained above, but also the maximum equalizer gain of the A6 EQ category if it exceeds 0 dB total
gain. This is essential to avoid the A6 limiter getting triggered.

 1.7 Tutorial 5 – Protection and Limiter
KCS is dedicated to operate loudspeakers in the large signal domain and drive them close to their
physical limits. Therefore, it must comprise protection systems to avoid any damage. The states to
be monitored and limited are excursion, peak voltage, temperature and electrical power. The
values of these limits depend on the target platform, the target amplifier, the speaker and limits set
in the KCS-ID measurement module. They are set automatically on the KCS Server.

However, some of these limits might have to be adjusted manually. This tutorial explains briefly how
the protection systems and the limiter works and how to adjust the according parameters.

 Excursion Temperature U limit
 limit limit CU threshold Release Speed

 Audio Signal Equalizer
 Alignment Protection Linearization Output Limiter
 (e.g. A6)
 KCS Audio Path

 1.7.1 Short Theory

Klippel R&D System KCS Monitor Tutorial  7

Mechanical Protection System
If the anticipated peak displacement is about to exceed
the mechanical limit, the low-frequency signal
components in the audio signal are attenuated by an
adaptive linear filter.
The advantage of using an adaptive linear filter is that it
does not produce nonlinear distortion, like a limiter
would. Even in the moment of activation, minimum
artifacts are produced, especially when some look-
ahead delay is applied.

Thermal Protection System
If the voice coil temperature is about to exceed the
thermal limit, the complete audio signal will be
attenuated for a short time.
See the transfer function of the attenuation behavior
vs. frequency on the right.

Voltage Limiter
The output voltage limiter is the last element in the KCS processing. It is intended to avoid amplifier
clipping. If KCS detects a higher output voltage than the specified maximum voltage U limit:
 1. The limiter activates the mechanical protection system (adaptive filter attenuating low
 frequencies).
 2. If the mechanical protection is already attenuating low frequencies by more than the
 absolute value of CU threshold, the limiter also triggers the thermal protection and reduces
 the overall audio gain of the complete system.
The Release Speed defines the protection system deactivation speed in dB/s.

Attention: To be able to achieve minimum latency of the complete KCS processing, the limiter does
not use a look-ahead delay. Hence, due to the very fast reaction in the moment the limiter activates,
a short audible artifact might be produced. In a frequency sweep measurement, this would be
detected as Rub&Buzz.

In a future KCS release an optional look-ahead delay will be available to reduce the audibility on
limiter activation in applications where an additional delay is tolerable.

 1.7.2 How to Setup Protection and Limiter
Note: See [KCS4] KCS Evaluation Tutorials for tutorials on how to perform impulsive distortion
measurements and how to treat Rub&Buzz issues.

Excursion Limit
There are several reasons why the maximum excursion might be reduced in the KCS Monitor.

8  KCS Monitor Tutorial Klippel R&D System

1. Transducer produces Impulsive Distortion
 Xmax is determined during KCS-ID using an imported target excursion value and using an IDR
 (Impulsive Distortion Ratio) measurement. It can happen that the IDR limit in KCS-ID was set
 too low or was deactivated. In addition, it is not very sensitive for certain irregular distortion
 such as air flow noise.
 If audible impulsive or other irregular distortion (e.g. Rub&Buzz) is produced by the
 transducer during evaluation (subjective and objective tests), reducing the Excursion Limit
 can increase sound quality.
 2. Amplifier is not sufficient
 If the maximum excursion Xmax set by KCS-ID/KCS Server cannot be reached with the used
 amplifier due to insufficient peak voltage, the voltage limiter will activate frequently to avoid
 amplifier clipping.
 As a limiter can degrade the perceived sound quality due to its inherent nonlinear behavior,
 it can be beneficial to limit Xmax. Especially if a significant bass boost is applied (maximum
 gain > 10 dB) so that a major part of the voltage needed to reproduce broadband signals is
 used at low frequencies, reduce the Excursion Limit to lower peak voltage requirements.
 Good indications showing that the amplifier is not sufficient for achieving Xmax is that
  ‘KCS Output Limiter active’ in the State window pops up regularly
  u out peak in the Voltage and Current window is regularly reaching the U limit value
  displacement is always significantly (>10 %) below the protection limit Xprot
 indicated by the bold red lines in the Displacement window, even when the amplifier
 voltage is at its limits

Thermal Protection
A conservative default limit is set automatically on the KCS Server. Anyway, make sure that it is
below the maximum rating of your transducer. Note that the limit value is a temperature increase in
the unit Kelvin, referenced to the temperature during the KCS-ID measurement. It should be
adjusted if better values are provided by the transducer manufacturer. Anyhow, choose a
conservative value as the voice coil heats up nonhomogeneous, but the thermal protection relies on
an average coil temperature.

Output Voltage Limiter
Default values for the limiter are set automatically on the KCS Server if the maximum voltage of the
power amplifier is known, for instance the KA3’s AMP card, the APE evaluation board and the NAD
platform. In this case usually the limiter setup parameters do not have to be changed. However, in
some cases manual adjustments as described in the passages below might increase the system’s
performance:

If a strong bass boost is performed (>12 dB maximum gain), the major part of the total voltage is
used at low frequencies for broad-band signals. Then CU Deactivation can be set to a high negative
value (-6 … -12 dB) and the limiter will mainly attenuate low frequencies. If no significant bass boost
is performed (

 reducing the bass boost (using alignment filter of high order, increasing cut-off frequency)
  reducing the Excursion Limit (see section above)

Note: Limiter activation is indicated by a warning ‘KCS Output Limiter active’ popping up for a short
time in the State window.

 1.7.3 Protection with separate ANC input channel
On certain special KCS configurations a dedicated input channel for active noise cancellation (ANC) is
available. In ANC applications the latency of the signal has to be minimized in order to reach the
desired cancellation effect.

The ANC signal is provided to KCS via a separate input channel to avoid unnecessary digital filters (EQ
/ Alignment) adding group delay to the signal. Also, a dedicated speaker protection system for ANC is
used with ultra-short latency (0.1 ms) while the audio protection system has a larger, configurable
latency to minimize audible artifacts.

 Audio Signal
 Equalizer
 (e.g. A6)
 System
 Alignment
 Audio
 Protection + Linearization
 Output
 Limiter

 ANC Signal Low-pass ANC
 1.5kHz Protection
 KCS Audio Path with ANC

Note: The fixed low-pass filter in the ANC Signal is only available upon special request and is
preferably applied externally prior to any KCS processing. The currently implemented 4th order
Butterworth filter at 1.5kHz adds 0.3 ms group delay to the ANC processing.

 Voice Coil Displacement
 xoffset currently not updated
 xpeak xbottom xDC xoffset xprot -xprot
 xpeak anc xbottom anc
 1,5 KLIPPEL

 1,0

 0,5
 X [mm]

 0,0

 -0,5

 -1,0

 -1,5
 74850 74900 74950 75000 75050 75100 75150 75200 75250 75300 75350
 Time [s]

10  KCS Monitor Tutorial Klippel R&D System

Right-click inside the voice coil displacement chart and select “Show all curves” to see the
 separate displacement caused by the ANC input signal only. The ANC displacement budget is
 fixed to 70% of the available displacement working range (xprot).

 Protection
 20:56:26
 G cx (mechanical) G cu (thermal) G cx anc (mechanical) G cu anc (thermal)
 0
 KLIPPEL

 -5

 -10
 [dB]

 -15

 -20

 74850 74900 74950 75000 75050 75100 75150 75200 75250 75300 75350
 Time [s]

In the Protection Chart, the audio and the ANC signal attenuation gains are shown separately. If the
assigned ANC budget is exhausted, the ANC protection is activated.

Note: As the ANC protection is configured for ultra-short latency (0.1 ms), the attack of the
protection attenuation could produce audible artifacts. It is recommended to avoid activating the
protection of the ANC signal by adjustment of the respective ANC system used (G_cx_anc should
stay at 0 dB).

If the assigned ANC budget is not completely used, the free displacement working range is available
for audio reproduction.

Please contact kcs-support@klippel.de in order to discuss and optimize the strategy for ANC
protection in context of a particular ANC over-all system design.

Klippel R&D System KCS Monitor Tutorial  11

2 KCS Monitor Reference

 2.1 KCS Setup Parameters
This section describes the available parameters to change the KCS setup. These parameters can be
found in the Properties of the KCS Monitor operation. See the simplified signal flow charts and setup
parameter descriptions below.

Signal Flow – KA3
 Excursion Temperature/ Voice Coil KCS Audio
 f0 type U limit
 Limit Power Limit Stabilization Path
 Protection Release CU Power
 Audio Delay Speed threshold
 Audio Gain Amplifier
 Signal Mirror
 Crossover Alignment delay Protection Limiter
 Filter
 Tweeter Protection Tweeter
 Gain Delay Delay
 delay delay

Signal Flow – NAD platform

 f0 type
 Excursion Temperature/ Voice Coil KCS Audio
 Limit Power Limit Stabilization U limit
 Path
 Audio Protection Release CU Power
 Gain Delay Speed threshold
 Audio Amplifier
 Signal Mirror
 A6 Alignment delay Protection Limiter
 Filter

KCS Processing – Setup Parameters
Note that not all parameters are available on every hardware platform.
Audio Gain
 Change the gain at the input stage of the KCS real-time processing.
Relative Tweeter Gain
 Change the gain of the tweeter channel relative to the woofer channel. Note that the Audio
 Gain changes the level of both woofer and tweeter channel.
Tweeter Delay
 Adjust the delay of the tweeter channel relative the woofer channel delay.
Crossover
 Choose a crossover filter from the drop-down list if the speaker under control shall only be
 used up to a certain frequency or if a tweeter channel shall be used. Important: If the target
 bandwidth in the KCS-ID was not set to fullrange, the KCS Server will automatically apply a
 crossover filter. Do not increase the frequency in this case as the speaker parameters were
 not identified above this frequency as this can cause unpredictable behavior.
Alignment
 Define a new target frequency response. Based on the initial KCS data, a pre-filter is
 calculated automatically to achieve a target response with 2nd, 4th or 6th order high-pass
 characteristic with a desired cut-off frequency f0. See 2.3 for more information.
Excursion Limit

Klippel R&D System KCS Monitor Reference  13

The initial parameter identification (KCS-ID and KCS Server) defines a certain excursion limit
 Xmax. In some cases this value might be too high because peak amplifier voltage is not
 sufficient or impulsive distortion is audible. See 1.7 for more information.
Temperature Limit
 This defines the temperature at which the thermal protection reduces the overall audio gain
 by G cu (see 2.2.6). The temperature limit value is defined as a temperature increase in
 Kelvin. 0 Kelvin corresponds to the temperature at which the initial identification (KCS-ID)
 was performed.
Power Limit
 If the electrical power is about to exceed this limit, the thermal protection system is
 activated and reduces the overall gain for a short time.
Protection Delay
 A delay of the audio signal in the mechanical protection system is applied to reduce audible
 artifacts caused by protection system activation.
Limiter Settings
 The output voltage limiter is intended to avoid amplifier clipping. If a higher output voltage
 than the specified maximum voltage U limit is detected, the limiter activates the mechanical
 protection system which applies an adaptive high-pass filter. If the mechanical protection is
 attenuating low frequencies by more than the absolute value of CU threshold, the thermal
 protection system is activated additionally reducing the gain of the complete system. The
 Release Speed defines the limiter deactivation speed in dB/s. See 1.7 for detailed
 descriptions how to set up the limiter.
Voice Coil Stabilization
 With active voice coil stabilization a small DC voltage will be applied to keep the voice coil
 always at its initial rest position. The stabilization should always be active. However, it can
 be useful to deactivate it to for demo and evaluation purposes.
Store Initial KCS Data in Flash/Clear Flash
 On some hardware platforms like the APE Evaluation Board, the initial KCS data may be
 stored in persistent memory to allow standalone application. When persistent data is
 available the KCS will automatically start when powering the hardware, a PC connection is
 not required. For using this feature, KCS Monitor must be connected to the device and KCS
 must not be running. Note that there is only one initial data slot. Storing another data set
 will overwrite an already stored set.

KCS Monitor – Display Parameters
Import Bl(0)
 Bl(0) is the transduction factor between electrical current and mechanical force at the rest
 position X=0. The KCS Monitor needs this value for calibrating relative digital KCS
 parameters into the physical domain. This allows to display voice coil displacement in mm
 and mechanical stiffness in N/mm instead of relative parameters, e.g. X/Xmax or
 Kms(X)/Kms(X=0). The value of Bl(0) is identified on the KCS Server if the KCS-ID was
 performed using a laser sensor or if a Bl(0) was imported in the KCS-ID. If no mechanical
 calibration was done on the KCS Server, Bl(0) is empty and only relative parameters are
 displayed.
Set Time Window
 Limit the number of history records which are displayed in all charts with time x-axis. One
 history record corresponds to one second.
History Memory
 Set the number of history records which should be stored in the operation. Not available in
 standard KCS Monitor which stores always 30 minutes of data.
KCS Monitor Demo View

14  KCS Monitor Reference Klippel R&D System

This activates the non-pro KCS Monitor look which might be preferred when doing demos.
Reset Laser Position
 Reset laser signal back to the zero-position.

 2.2 Result Windows
This section explains the content of the different result windows. The result windows have a lot of
similarities to the LSI3 windows.

 2.2.1 Nonlinear Curves

See Manual LSI3 for information about the nonlinear curves such as Bl(x) and Kms(x).

 2.2.2 x(t) Displacement

Klippel R&D System KCS Monitor Reference  15

The window Displacement shows the absolute voice coil displacement over time. This information is
e.g. important for evaluating the functionality of the mechanical protection system. The green
curves represent the positive and negative peak displacement.
The control system also identifies voice coil rest position changes due to nonlinear parameters,
visco-elastic effects, a leaky box or other reasons which is essential for realizing a reliable mechanical
protection system. Voice coil rest position changes are indicated by the xOffset curve. Note that if
the DC Stabilization is active, this curve should be close to zero at any time.

 2.2.3 u(t) Voltage, i(t) Current

The voltage and current signals are essential for dimensioning a proper amplifier for the particular
application. For amplifier evaluation, it is very useful to evaluate the peak values of voltage and
current with different signals (e.g. different music signals, speech) and different alignments for
verifying that the amplifier is sufficiently dimensioned, esp. in regards to peak voltage capability. For

16  KCS Monitor Reference Klippel R&D System

real audio signals such as music and speech which comprise a high crest factor, the peak voltage and
current is usually the limiting factor of the amplifier.

The curves u rms, u peak (hidden curve), i peak and i rms are signals which are measured by the
sensors in the hardware device. These signals are not recorded in full audio sampling frequency but
are low-pass filtered and decimated (usually to 6 or 12 kHz, see Setup window  Sampling
Frequency Detector) to lower DSP processing requirements. Hence if higher frequencies are
reproduced, these signals can comprise a significant error.

The u out peak (sim) curve shows the peak voltage at the output of the KCS processing at full audio
sampling frequency, multiplied with the gain between its output and the amplifier output. This value
represents the output voltage of the amplifier very accurately if
 1. the gain of the amplifier is constant (which is a requirement for KCS processing anyway) and
 2. the amplifier is not clipping. The latter can be avoided by activating the KCS output limiter.

 2.2.4 ∆Tv(t)Temperature, P(t) Power

This window shows the increase of the voice coil temperature TV and the electric input power P(t)
versus time. This information is very helpful to verify that the transducer’s power handling and the
amplifier dimensioning is sufficient.

Klippel R&D System KCS Monitor Reference  17

2.2.5 fs(t) Resonance Frequency

This result window shows the speaker’s resonance frequency fS (t, x=0) or fC (t, x=0), the stiffness of
the mechanical suspension Kms (t, x=0) or Kmt (t, x=0) at the rest position x = 0.
At high excursions the mechanical stiffness Kms (and hence the resonance frequency) at the rest
position usually decreases. The information shown in this window quantifies the degree of time-
variance of the parameters of the particular DUT with a particular stimulus.
Note that the identified parameter changes are compensated by Nonlinear Control. Hence the
variations do not have any impact on the frequency response of the KCS active speaker system.

 2.2.6 Distortion Components

18  KCS Monitor Reference Klippel R&D System

The relative distortion components describe the ratio of the peak values of the equivalent input
distortion generated by the selected nonlinearities and the peak value of the total signal.
The equivalent input distortion is identical to the voltage that is required to compensate the
particular nonlinearity.

 2.2.7 Z(f,x=0) Impedance Magnitude

The impedance magnitude is calculated based on the identified linear speaker parameters.

 2.2.8 Protection

The activation of the mechanical and thermal protection systems can be observed at any time. The
attenuation value G cx (mechanical) indicates an approximate value at which degree low frequencies
are attenuated. The attenuation value G cu (thermal) indicates the attenuation value of how much
the whole audio signal is attenuated. See more information in the tutorial 1.7.1.

Klippel R&D System KCS Monitor Reference  19

You can view the absolute displacement curve over time for evaluating the functionality of the
mechanical protection system. The voice coil temperature can be observed in the window Electrical
Power and Temperature.

 2.2.9 H(f) Sound Pressure

This window shows the predicted small signal sound pressure transfer function of the target system
before and after applying the pre filter Hpre(f) which contains a linear alignment filter and a linear
inductance compensation filter. The transfer functions are normalized so that a gain of 0 dB at high
frequencies is reached for a virtual loudspeaker system without inductance. See 1.6 and 2.3 for
detailed information.

Magnitude/Phase KCS OFF
 Relative sound pressure transfer function of the identified driver without any pre-filtering
Magnitude/Phase KCS ON/EQ
 Relative target sound pressure transfer function corresponding to the chosen alignment
Magnitude/Phase Fixed Point
 If fixed point arithmetic is used for the filter implementation (e.g. on NAD platform), this
 curve displays the realizable transfer function with the given coefficient accuracy. A warning
 is displayed on the KCS Monitor’s Properties if the curve differs significantly from the target.
Magnitude/Phase Hpre(f)
 Magnitude of the pre-filter used to realize the target transfer function

20  KCS Monitor Reference Klippel R&D System

2.2.10 Linear Speaker Parameters

This table shows the speaker’s linear parameters at the cursor position and of the initial data.

Klippel R&D System KCS Monitor Reference  21

2.2.11 State

The State window gives information about the current controller states, information about the
measurement, modeled and measured transducer states and electrical parameters at the current
position of the time cursor.

If KCS is running, also the control mode can be changed using buttons at the top of this window (see
1.5).

Note: It is not recommended to hide this window as important errors and warnings are displayed
here.

22  KCS Monitor Reference Klippel R&D System

2.2.12 Setup

You find additional information about KCS setup, hardware platform and initial KCS data here.

 2.3 Alignment
This section describes the filter types available for the high pass filter alignment. See 1.6 for practical
tips how to use this feature and to incorporate it in the system tuning process.

Second Order Alignment
Only available for 2nd order systems (sealed boxes or transducer in free air). Replaces the given
systems resonance frequency and Q-factor by a desired cut-off frequency and Q-factor.
The target transfer function is defined as
 
 , ( ) = 
 + + 
with Q denoting the target quality factor and the desired cut-off frequency in radians.

Butterworth and Chebychev Alignments
These alignment types are available as 4th and 6th order filter types. The target transfer function for a
Chebychev alignment is defined as

Klippel R&D System KCS Monitor Reference  23

 
 
 , ( ) =
 ( − − ) ( − − )
 ∏ 
 = ( − ( − ))
 
with k denoting the Chebychev parameter, N the order of the filter and the desired cut-off
frequency in radians. The Butterworth response is equal to the Chebychev response with k set to
one. The poles are a spread in equal distance over a circle in the complex plane.

Bessel Alignments
Bessel alignment types are available as 4th and 6th order filter types. The target transfer function of
order N is defined as
 ∗ 
 ( )
 
 , ( ) = 
 ∗ ( − )!
 ∑ = ( ) − ! ( − )!
 
Contrary to the other filter types, the cut-off frequency does not describe the 3dB decay from the
pass band gain but a correction factor is introduced to reach this behavior. The correction factors
for 4th and 6th order filters are
 4 = 0.47306, 6 = 0.36991.

Comparison of different Filter Types

 th
Magnitude and Phase of the target responses for various 4 order alignments with a cut-off frequency of 100Hz.

The curves shown above display magnitude and phase of all available 4th order alignments. While all
transfer functions result in a decay of 20dB per octave, the filter type determines how fast this slope
is reached below the cut-off frequency. A Chebychev alignment with k = 0.33 will reach -40dB
attenuation around an octave higher than its counterpart with k= 0.7. This causes a higher pass-band
ripple and faster changing phase shift resulting in a higher group delay, though.
The 6th order alignments show similar behavior reaching slopes of 40dB/octave, but exhibit higher
phase shifts (360°) and group delays.

24  KCS Monitor Reference Klippel R&D System

2.4 Hardware Connection
 2.4.1 Klippel Analyzer 3
The minimal hardware setups on the KLIPPEL KA3 comprising one SPEAKER CARD, one LASER CARD,
one XLR CARD and an optional AMP CARD is illustrated in the figures below. For more Information
about the hardware, please see the Hardware Manual [Hardware].

Hardware connection on KA3 without AMP Card

Hardware connection on KA3 with AMP Card

Note: Laser and microphone sensors are not necessarily required for operating the KCS. However,
these sensors are recommended for evaluating its performance, such as nonlinear distortion
reduction and mechanical protection system. In addition they are necessary for performing
measurements on the transducer, such as irregular distortion (‘Rub&Buzz’) measurements. The laser
is particularly useful for identifying the force factor Bl(X=0) prior to operating the KCS.

Klippel R&D System KCS Monitor Reference  25

2.4.2 Nuvoton Audio Development Platform
Perform the following steps and connect the hardware according to the following pictures.
 1. Make sure the D11 jumper removed if using NAU83G10 and connected if using NAU83G20
 2. Connect the speaker. Make sure the polarity is correct.
 3. Connect the power supply. If you change or reconnect the speaker later, unplug the power
 supply before to avoid hardware failure due to accidental shorting of pins.
 4. Connect USB to the PC
See Nuvoton’s NAD Quick Start Guide for more information.

NAU83G10

NAU83G10: Do not use a power supply with a voltage higher than 5.5V. This would damage the chip.

NAU83G20

26  KCS Monitor Reference Klippel R&D System

2.5 Things you should never do
Although we tried to organize the user interface to avoid misuse, you should be aware of the
following:

Never mismatch parameters and loudspeakers
Parameters identified on a particular loudspeaker model can usually not be used to control a
different loudspeaker model unless the linear and nonlinear parameters of both loudspeakers are
very similar.

Note: Every initial data set has two unique 8-character identifiers KCS-ID Identifier (assigned by the
KCS-ID operation) and Initial Data Identifier (assigned by the KCS-Server) which are displayed in the
window Setup.

Never change the enclosure
The controller can be used with loudspeakers operated in free air as well as with vented and sealed
enclosures. This information is entered before starting the Initial Identification (KCS-ID). Changing
the type of the enclosure type or size requires a new KCS-ID Parameter Identification creating a new
set of initial parameters.

Never change the polarity
Usually, loudspeaker parameters have an asymmetric characteristic making the polarity of the
connections at the loudspeaker terminals critical for the compensation of nonlinear distortion.
Never change the polarity after Initial Identification as this will lead to additional nonlinear distortion
and a wrong identification of the voice coil rest position.

Klippel R&D System KCS Monitor Reference  27

2.6 Troubleshooting
 2.6.1 Message Boxes
Connect to device failed
Make sure the correct KCS device is connected to the PC. Select another COM port and connect
again.

Running measurement on device
This message appears if the KCS Monitor operation is started and a KCS on-line session is already
running on the hardware device. Press ‘Yes’ if you would like to overwrite the initial data stored on
the device and start a KCS session. Press ‘No’ to terminate the control session which is running on
the device. In this case the KCS Monitor operation stays untouched. If the operation is started ,
the initial data stored in this operation is written to the device and the KCS on-line processing is
started.

Uploading Data from Device
If the KCS Monitor operation does not hold any initial data but the connected device does, you have
the possibility to upload initial data from the device to the KCS Monitor operation or to delete the
initial data on the device.

 2.6.2 Selected warning messages
The warning messages are shown in the KCS Monitor’s State window.

Output clipping
Cause: The output of the KCS on-line processing exceeds approx. -0.5dB of the expected maximum
output voltage.

28  KCS Monitor Reference Klippel R&D System

Remedy: Decrease audio level, decrease the Excursion Limit or activate the limiter in the Properties.

Note: If this warning is displayed, audible artifacts due to clipping can occur.

Even if this warning is not displayed, clipping can occur because the exact maximum ratings of the
connected hardware are not always known (e.g. maximum rail voltage depends on connected PSU).

External input signal is limiting. Reduce audio input level to avoid clipping.
Cause: The input of the KCS on-line processing (before or after the KCS audio gain stage which value
is defined in KCS Monitor’s Properties) exceeds approx. -0.5dBFs.
Remedy: Check the IN level in the window State. If it is close to 0dB, reduce the input level. You
might increase the KCS audio gain in the KCS Monitor property page (Audio Gain slider). Make also
sure that IN level plus audio gain level is not exceeding 0dB.

Note: If this warning is displayed, audible artifacts due to clipping can occur.

Temperature too high
Cause: The measured increase of the voice coil temperature exceeds the limit defined in the KCS
Monitor’s Properties.
Remedy: Make sure that a speaker is connected and the correct initial data for the particular DUT is
loaded.

Insufficient Bl(x) decay. No x-offset updating possible!
Cause: For identifying the voice coil rest position, KCS evaluates the nonlinear distortion found in the
measured current signal caused by the nonlinear Bl(x) speaker characteristic. If the Bl(x) decay is too
small, voice coil position identification will not work:
Remedy: Use a driver with more nonlinear Bl(x) curve or, if possible, relax the limits in the KCS-ID
(e.g. increase the target excursion).

Note: KCS will work anyway, but higher safety margins for the maximum allowed excursion are
required because the exact voice coil position is not known. Active voice coil stabilization will not
work if this warning is displayed.

 2.6.3 Other Issues
Bad Audio Quality – Impulsive distortion
See section How to treat Rub&Buzz Issues in [KCS2] KCS Evaluation Tutorials.

Lack of Bass
 1. Set an alignment (see 1.6) with an appropriate frequency fc.
 2. Mechanical Protection System is active (see 1.7). In this case reduce the audio gain.

Contact kcs-support@klippel.de if you cannot solve any KCS issues or have other questions.

Klippel R&D System KCS Monitor Reference  29

R
 3 Index Requirements.................................................................. 1
 Result Windows ............................................................ 15
 ∆
∆Tv(t)Temperature, P(t) Power .................................... 17
 S
 Selected warning messages .......................................... 28
 Setup ............................................................................. 23
 A Short Theory ................................................................... 7
Alignment ..................................................................... 23 State .............................................................................. 22

 D T
Distortion Components................................................. 18 Temperature too high ................................................... 29
 Things you should never do .......................................... 27
 Troubleshooting ............................................................ 28
 F Tutorial 1 – Starting KCS.................................................. 2
fs(t) Resonance Frequency ........................................... 18 Tutorial 2 - Viewing data ................................................. 3
 Tutorial 3 – Switching Control Modes ............................. 4
 Tutorial 4 – Alignment and Equalization ......................... 5
 H Tutorial 5 – Protection and Limiter ................................. 7
H(f) Sound Pressure ...................................................... 20
Hardware Connection ................................................... 25 U
How to Setup Protection and Limiter ............................. 8
 u(t) Voltage, i(t) Current ............................................... 16

 I
 X
Introduction .................................................................... 1
 x(t) Displacement .......................................................... 15

 K
 Z
KCS Monitor Reference ................................................. 13
KCS Monitor Tutorial ...................................................... 1 Z(f,x=0) Impedance Magnitude ..................................... 19
KCS Setup Parameters .................................................. 13
Klippel Analyzer 3 ......................................................... 25

 L
Linear Speaker Parameters ........................................... 21

 M
Message Boxes ............................................................. 28

 N
Nonlinear Curves .......................................................... 15
Nuvoton Audio Development Platform ........................ 26

 O
Other Issues .................................................................. 29

 P
Protection ..................................................................... 19
Protection with separate ANC input channel ............... 10

Klippel R&D System Index  31